Question

I’m trying to find the sum of specific values within a table, using SQL. A sample table is:

+-------+-------+-------+-------+-------+-------+-------+
|  ID   |  Co1  |  Va1  |  Co2  |  Va2  |  Co3  |  Va3  |
+-------+-------+-------+-------+-------+-------+-------+
|  01   |  AA1  |   23.0|  AA2  |   11.2|  AA3  | 328.34|
|  02   |  AA2  |   27.0|  AA3  | 234.56|  AA4  |   23.8|
|  03   |  AA1  | 409.01|  AA4  | 234.98| NULL  | NULL  |
+-------+-------+-------+-------+-------+-------+-------+

I have 35 such ‘Code’ columns and values.

What I need is selecting a table having only one code. Say I need Code AA3, this would be (the Code column is not required here, but only to show where I got the values):

+-------+-------+--------+
|  ID   | Code  |  Value |
+-------+-------+--------+
|  01   |  AA3  |  328.34|
|  02   |  AA3  |  234.56|
|  03   |  AA3  |       0|
+-------+-------+--------+

And I will later need another (separate) query which contains the sum of several codes, for example the sum of codes AA1 and AA2 together.

+-------+---------+
|  ID   |   Value |
+-------+---------+
|  01   |     34.2|
|  02   |     27.0|
|  03   |   409.01|
+-------+---------+

I was thinking about having a ‘WHERE’ and run on every 35 columns, but that would really be tedious and this does not seem too efficient. I was wondering if there was a way to do that through SQL (I can do it with Excel with an if statement and it works wonders).

Maybe if there was a way to ‘search’ through a row, return the column name and then use that column name to retrieve the number?

Let me know if you require more information =)

Answer 1

What you should do is store your data in a normalised form.

However…

select SUM(v)
from
(

select * -- ID, r, v 
from 
(select * from yourtable) u
unpivot
( r for co in (co1, co2, co3)) as u1
unpivot
(  v for va in (va1, va2, va3)) as u2
where RIGHT(co,1) = RIGHT(va,1)
) v
WHERE R = 'AA1' -- etc

will return the results you seek